Dietary patterns and the risk of breast cancer in Japanese women

<jats:p>Components of the Japanese diet that might contribute to the relatively low breast cancer incidence in Japanese women have not been clarified in detail. To evaluate associations between broad dietary patterns and breast cancer risk in a Japanese population, the authors conducted a case–control study using data from the hospital‐based epidemiologic research program at Aichi Cancer Center (HERPACC). Factor analysis (principal components) was used to derive food patterns based on the 31 food variables and allowed designation of four major dietary patterns: <jats:italic>prudent</jats:italic>, <jats:italic>fatty</jats:italic>, <jats:italic>Japanese</jats:italic> and <jats:italic>salty</jats:italic>. In total, 1885 breast cancer cases were included and 22 333 female non‐cancer patients were recruited as the control group. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were determined using multiple logistic regression analysis. After adjusting for potential confounders, there were no clear associations between the <jats:italic>fatty</jats:italic>, <jats:italic>Japanese</jats:italic> or <jats:italic>salty</jats:italic> dietary patterns and overall breast cancer risk. In contrast, an inverse association was evident for the <jats:italic>prudent</jats:italic> dietary. Women in the highest quartile of the <jats:italic>prudent</jats:italic> dietary pattern scores, had a 27% decreased risk of breast cancer compared with those in the lowest (95% CI: 0.63–0.84, <jats:italic>p</jats:italic> for trend < 0.0001). In addition, for women with a body mass index ≥25, the highest quartile of the <jats:italic>fatty</jats:italic> factor score was associated with a 58% increment in breast cancer risk compared to the lowest quartile, with a significant linear trend (<jats:italic>P</jats:italic> = 0.027). The authors found the <jats:italic>prudent</jats:italic> dietary pattern to be negatively associated with breast cancer risk. In addition, the <jats:italic>fatty</jats:italic> and <jats:italic>Japanese</jats:italic> patterns may increase breast cancer risk among obese women. (<jats:italic>Cancer Sci</jats:italic> 2007; 98: 1431–1438)</jats:p>